1. Field of the Invention
This invention relates to heat shrinkable wraparound articles for covering elongate objects such as pipes or cables, or joints therebetween.
2. Introduction to the Invention
Heat shrinkable polymeric or fabric based articles are well known. Typically the articles are in the form of sleeves which possess the property of being able to shrink to smaller diameters when heated. Such a sleeve is constructed with a diameter large enough so that it can conveniently be placed about a substrate, and then it is heated, the heat causing it to shrink to conform to the substrate.
The heat shrinkable sleeves may be closed in cross-section, but, for ease of application inter alia they are preferably wraparound. Examples of such wraparound sleeves are described, for example in U.S. Pat. No. 3,455,336 (Ellis), and in U.S. Pat. No. 4,200,676 (Caponigro, Lopez), U.S. Pat. No. 4,586,971 (Wallace), EP 0163508 (Leest, Peigneur, van Beersel), U.S. Pat. No. 4,359,502 and JP 54-149780 (appno 53-59167).
In the above described wraparound heat shrinkable sleeves, the so-called closures for holding the wraparound closed, i.e., for holding the mating or overlapped ends of the sleeves together, may be mechanical, for example as described in U.S. Pat. No. 3,455,326, or based on direct bonding e.g. by adhesive or fusion, e.g. as described in U.S. Pat. No. 4,200,676 or in JP 54-149780. Where they are based on bonding to, or by, overlapped edges, it is typical to use a laminar panel or patch to bond to the overlapped edges. In these cases it is desirable not only to heat the article to shrink it, and perhaps also to activate an adhesive on the patch, but also to "pat" the patch, i.e. to provide a downward pressure on the patch, typically with a gloved hand, in order to form a good bond. Similarly where direct fusion is used to bond directly overlapped edges, it is typical to leave a section of the sleeve uncoated with adhesive to enable the sleeve (typically polyethylene) to bond to itself. In this case also a downward pressure onto the bonded area is desirable. In these applications it is also necessary to prevent the sleeve ends from slipping relative to each other, causing the wraparound sleeve to open. In certain situations application of a downward pressure and prevention of sleeve end slippage is difficult, if not impossible to achieve.